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Discussion Starter · #1 ·
Yeah - you read that right and no, I wasn't sure if this was the place to pose that question. I realise it's hardly a pressing issue, but it's something I've often wondered about.

As you'll see from my signature, I have two SL350's - a K0 and a K2. It's been a while now but from what I can remember, I put a later camshaft into the earlier bike (I think the original was pitted and/or comparatively it's a very heavy lump), and so with the exception of the starter motor they're essentially the same engine, with minor internal differences like piston dome shape and valve sizes. That being the case, I assumed they'd behave pretty much identically when it came to processes like combustion.

But when I run them they have very distinct exhaust smells about them. Until we have smellavision, I'm not going to be able to demonstrate what I'm talking about, but trust me when I say they're very significantly different. Not in a bad way - both engines have been rebuilt and run fine with no smoke and no burnt oil - but the odours aren't the same.

I assume it's probably got something to do with the carburation: the K0 has vacuum slide Mikuni carbs whereas the K2 has cable slide Kehins. I s'pose it's possible they atomise fuel in different ways which results in a different exhaust composition, but I kinda thought fuel was fuel and that it just burns when ignited. And I guess that's why I'm not a chemist . . .

So whatd'y'all reckon?
 

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I'm thinking you may possibly have same fuel but different oil??
And out of curiosity.. how much "smelling" of exhaust fumes do you do???
 

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Discussion Starter · #3 ·
Ha.

As far as I can recall, it's the same oil - same brand, type, etc. I tend to buy in bulk.

As for breathing in fumes, it's most noticeable when I put the bikes into the garage after running around on them. Strange as it sounds, I'm not a big one for inhaling fumes for the fun of it . . .
 

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Is there anything weird about the smells, or just that they're different?

While I was chasing carb settings, one side used to to smell terribly like sour pickles. Same engine, and both sides smelled different. I remember reading something about things smelling caustic because of lean settings.
 

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Discussion Starter · #5 · (Edited)
Pickles, huh? That's very odd.

Nothing weird with my two - one just smells, I dunno, sweeter than the other. Thinking about it, all of my bikes have different smells to the exhausts. The 750 is different to the 450, which in turn is different to the 350's. All use the same gas, and all use the same oil.

I'd assumed the engine displacement and designs were a determining factor in how the bikes smell when hot - and to some degree, I still think they are - but that doesn't explain the disparity between the 350's. Not that I'm complaining you understand . . . it's another thing that gives them different characters.
 

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No 2 bikes will ever be exactly the same.

Different oil, different gas (even the same gas on different day), condensation, ambient temperature, contaminants, fuel or oil additive or residue, different exhaust or mufflers... All can add up to make one engine's exhaust smells different than the next. Not to mention your own perception of said smell.
 
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